In a lens array unit used in an optical device, a light blocking film is disposed at an area between adjacent lenses to absorb stray light. Such an optical device can be employed in an image processing apparatus such as a printer, a copier, a multifunction printer (MFP), a facsimile, a scanner, a liquid crystal display device, a solid-state imaging device, a multiple image transmission device of an optical interconnection system, and a confocal laser microscope. In addition, a technology of such a lens array unit can be applied to an optical communication field, an optical disc field, an image display field, an image transmission-connection field, an optical measurement field, an optical sensing field, an optical processing field, and the like.
A method for forming such a light blocking film includes a method of printing black ink, which can be cured by ultraviolet rays, on the area between the adjacent lenses and then curing the ink, a method of developing the film and removing a portion of the film by a photolithography, and the like.